Remote switches are used in many applications to control the operation of multiphase electric motors. Generally, switches must be capable of energizing a motor in either a forward or reverse direction. In other operations, the switch must be capable of operating the motor between one or more speeds, both in the forward and reverse directions.
In the construction of electric motor switches, it is preferred that the switch be both simple in construction and protect against simultaneous operation of the switch in both the forward and reverse directions. It is readily appreciated that if a switch is capable of simultaneous operation in both directions, severe damage can be imparted to the motor controlled by the switch. Thus, this feature is extremely important in switch design. In the past, to accomplish automatic interlocking to protect against simultaneous operation of the motor in both directions, switch designs have been overly complex requiring substantial interrelated wiring to accomplish the desired goal. The complexity of switch design is compounded when a two speed switch must be provided. While this is readily accomplished, switches designed to do so in a way eliminating the possibility of simultaneous operation in both directions have been overly complex involving substantial cross wiring and thus additional components. This complexity has added to the cost, as well as the difficulty in repair and inspection of such switches.
An example of a two speed switch providing both forward and reverse directional control is that manufactured by Square D. Electric Co. of Milwaukee, Wis. and identified as a TJ-2 microswitch. The complexity of such a switch is readily evident upon even a casual examination of the jumper wires required between various contacts employed in the switch unit. Similar complexity is found in a two speed cam operated switch identified as the PBC switch manufactured by Euclid Electric Co. of Madison, Ohio.
Therefore, a need has arisen for a two speed switch for forward and reverse control of electric motors which eliminates the possibility of simultaneous operation of both directions of the switch without requiring the complexity heretofore required by prior art units.